Fruits and vegetables

Common adulterants

• Malachite green (green vegetables, green chilli) — A dye used to make vegetables look fresher; not a permitted way to colour produce.
• Artificial colour on green peas — Added colour to enhance appearance.
• Rhodamine B on sweet potato — A dye; not permitted for colouring produce.

Warning signs

• Cotton that turns green after rubbing the outer surface of a green vegetable
• Colour separating from green peas into water
• Cotton absorbing red colour from sweet potato skin

Home checks

• Malachite green on green vegetables: Rub the outer green surface of a small part with a cotton piece soaked in water, and separately with one soaked in vegetable oil. If the cotton turns green, DART says this indicates malachite green. Alternatively, press a small part on moist white blotting paper; a colour impression indicates artificial dye. (Indicative only. A household test can give a false positive or false negative, and it cannot tell you the amount present or whether the food meets the legal standard. Only testing by an accredited laboratory confirms adulteration. Chlorophyll in natural produce can stain cotton slightly.)
• Artificial colour on green peas: Put a little green peas in a transparent glass of water, mix well and let stand for half an hour. Clear separation of colour in the water indicates adulteration. (Indicative only. A household test can give a false positive or false negative, and it cannot tell you the amount present or whether the food meets the legal standard. Only testing by an accredited laboratory confirms adulteration.)
• Rhodamine B on sweet potato: Rub the outer red surface with a cotton ball soaked in water, and separately in oil. If the cotton takes up colour, DART says this indicates rhodamine B. (Indicative only. A household test can give a false positive or false negative, and it cannot tell you the amount present or whether the food meets the legal standard. Only testing by an accredited laboratory confirms adulteration.)

Laboratory testing

To confirm adulteration, a sample must be analysed by a food testing laboratory using standard methods. A purchaser can have food analysed by a Food Analyst for a fee under section 40 of the Food Safety and Standards Act, 2006, but must tell the seller at the time of purchase; you can also report to the food safety authority, whose officers draw official samples. See the Food testing page for official lab directories. Pesticide residues on fruit and vegetables cannot be detected at home; they are governed by limits in the Contaminants, Toxins and Residues Regulations and checked in laboratories. Washing produce well is still a good habit.